How a Video Game Taught Me Mental Maths

Brad Matthews personal category

While I’ve never been great at maths, the subject, I have always been good with numbers.

But there were a few things I could never get my head around.

Percentages and fractions chief among them.

The way it’s taught in schools is either wrote memorisation—that 1/10th is equivalent to 10%—now remember that and a dozen other common fractions, or a convoluted way of converting that gets even trickier when you’re talking improper fractions like 2 and 7/4s—which I can now easily see is 375%.

How did I get my head around it?

By playing the Legend of Dragoon of course.

It’s my favourite game of all time. It has a beautiful and compelling story, excellent battle mechanics, perfectly suitable music for each area, and actually lives up to the nostalgic feels I get when I play it after all these years.

But it also taught me (in concert with my inquisitive brain) how to calculate percentages quickly, easily, and accurately in my head.


Well there is a mechanic in the game called ‘Guard’. When you guard, you regenerate 10% of your health and mitigate incoming damage by 50%.

I learned that you regenerate 10% of HP from the Prima Guide (the game, PlayStation One, and guide were all purchased second-hand)—I’d never have normally bought a guide.

This is what happens when you guard.
Legend of Dragoon Guard

As you can see, Dart used guard and is recouped 10% of his maximum health pool by doing so.

As someone who loved games, created my own worlds, documented my favourites by making websites, filling binders with notes, creating hand drawn maps, and planed to make my own games, I wondered whether 10% a good number, or if it should be more or less.

Some enemies hit like a truck, others barely tickle—I needed some numbers to determine whether 10% was fair.

What about 20%?

How do I find 20%?

Well logic dictates that it would be double 10%. I was already fine with maths so I had no trouble calculating that 122 HP (from the above example).

That’s too much you could heal up way too fast with that.

What about 15%?

How do I find 15%?

Well it’s half of 10% (5%) on top of the original 10%.

66 divided by 2 is 33. 66+33 is 99.

That’s when I realised I didn’t particularly want the game to be easier, 10% did feel about right.

But what if the game was harder.

What if you only recovered 7% when you Guard?

Well budding game designer/theorist Bradley was on the case.

I knew 5% was 33 from the above example, but 1 or 2 percent is nitty-gritty and awkward, how do I calculate that in my head?

Again logic to the rescue.

If 66 is 10% of 660 (100%), then it’s 1/10th. Breaking down 66 (10%) in the same way would give me X (1%).

So I moved the decimal in my head and realised 1% is 6.6. So 2% would be 12.2 (or 12 as the game rounds to nearest whole number).

So 33 (5%) + 12 (2%) would give me 45 HP when I’d Guard.

That might have made the game too challenging for 12 year old me (though I’d be keen for 5% now).

Then I started thinking more explicitly about the relationships between the numbers.

10% meant guarding 10 times from low HP would fill me up (excluding additional damage taken during each round)—that’s 1/10th.

20% meant guarding 5 times—1/5th each time.

15%, came out at 6(ish) times—1/6th each time.

7%, 14(ish) times so 1/14th each time.

Thanks to this game, maths has been easy.

When I need 3.5%, I find 10%, find 1% from the 10% and multiply that number by 3.5.

When I need 20.5% I find 10%, double it. Find 1% from the 10% and halve that. Add the two together.

You can get into fractions of a percent too.

All it took was some logic and a catalyst to get me thinking.

School was never going to do that, but Legend of Dragoon did.

Post 7/30 (30 day blogging challenge #2—writing quickly) [Over 30 minutes]

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